Is Urban India Going Underwater Again?

This is the first blog in a 3-part series. Read the second and third blogs here.

India is in the middle of the 2025 southwest monsoon, with the Indian Meteorological Department having forecast above normal rainfall. Staying true to this forecast, this year’s monsoon has already caused repeated cloudbursts in Himachal Pradesh, extreme rains across Rajasthan, and rising waters in the Ganga, leading to flood alerts across Prayagraj, Varanasi and Patna. With heavy rains occurring across many cities, how will India’s urban areas fare through the rest of the season?

Grey stormwater infrastructure, such as drains, pumps and outfalls, is frequently overwhelmed by high levels of stormwater runoff from roads and streets during heavy rainfall events. Not just Indian cities like Bengaluru, Hyderabad, Delhi or Mumbai, but cities across the world are flooding frequently, with the Global South facing higher flood exposure. With multiple and recurring failures of grey infrastructure globally, alternatives are now being sought. This includes natural ecosystems, such as lakes, wetlands and forests, and blue-green infrastructure like bioswales, rain gardens and parks. When integrated with grey infrastructure, these flexible, low-cost, nature-based solutions can support conventional stormwater management and flood mitigation efforts.

Cities across India continue to expand stormwater networks, de-silt channels and separate sewage and stormwater drains, all very necessary activities. Cities bear high costs to build and maintain these large-scale, grey stormwater infrastructure. Repeated floods indicate that these actions alone remain insufficient in this era of dense and rapid urbanization, climate uncertainty and variability. The first step to tackle India’s urban flooding problem is identifying the key factors behind it.

Building in the Path of Floods

During rain events, urban developments, including public infrastructure (bus depots, roads, metro rail, airports, etc.) located in low-lying areas (floodplains, lake beds), face increased flood risk. Such areas are typically high recharge zones as water follows the gradient of the land and drains into these vegetated, low-lying locations.

A WRI India study indicates that in India’s 10 most populous cities, 39% (462 sq.km) of new urban developments between 2000-2015 (within 20 km of the city center) have been on low-lying, vegetated, high or very high recharge potential zones (Figure 1).

Spaces like lakes, wetlands and forests function as natural infrastructure, absorb stormwater, and reduce runoff volume and speed, thus reducing flood risk. Destruction and encroachment of these spaces deteriorate the natural flood defense of cities. Analyzing satellite imagery of select locations in Chennai and Hyderabad shows that between 1970 and 2020, lakes have shrunk or been replaced by roads, residential neighborhoods or playgrounds. Such locations routinely flood as stormwater drains into these low-lying areas.

Paving the Way for Floods

Rainwater generally infiltrates into the ground, flows as surface runoff or evapotranspirates into the atmosphere. Urban areas with impervious surfaces eliminate infiltration and reduce evapotranspiration, thereby drastically increasing surface runoff. A study in the United States indicates that for every 1% increase in impervious surface area, there is a 3.3% increase in urban flood magnitude.

The continuous addition of buildings, roads and flyovers for urban dwellers in Indian cities often fails to account for adequate stormwater infrastructure. Large volumes of stormwater stagnate on these impervious surfaces, causing repeated flooding.

WRI India’s working paper reports that built-up cover has increased between 2000 and 2015 by 35% in 0-20 km of the city center (9% in Mumbai to 127% in Surat); built-up cover increased by 84% in 20-50 km from the city center (30% in Kolkata/Mumbai to 412% in Pune). Most of the 10 most populous cities in India have flooded repeatedly over the last five years (2020-2025).

Storms of Uncertainty

Climate change driven rainfall variability is increasing, with cities receiving rainfall equivalent to monthly/seasonal averages within a few days or even hours. Pre-monsoon rains have also intensified with this year being the wettest May on record for multiple cities, including Bengaluru, which received more than 300 mm of rain. The devastating 2018 floods in Kerala were triggered by rainfall in excess of 200% of the state’s seasonal average, most of the rain falling within a week. The Chennai floods in 2015 were preceded by 345mm of rainfall recorded on December 1 (average December rainfall for Chennai is 191mm).

The associated economic, human and social costs for floods are also immense. Damage from the Kerala floods is estimated at USD 3.56 billion (INR 27 thousand crore) and Chennai flood losses at around USD 3 billion (INR 22 thousand crore). Bengaluru’s 2022 floods affected its IT corridor with estimated losses of USD 25 million (INR 225 crores) after just one day of heavy rainfall and flooding. A 2025 World Bank report estimates that Indian cities can face losses of up to USD 5 billion every year from urban floods alone by 2030.

From Reacting to Building Resilience

Recognizing the growing severity of urban floods, the Fifteenth Finance Commission recommended an allocation of INR 2,500 crore under the National Disaster Mitigation Fund (NDMF) for seven major metropolitan cities to improve flood mitigation. Cities are also leveraging multinational funding, such as the World Bank initiative for Bengaluru’s stormwater management and water resilience. And robust area-based rainfall and flood warning systems in cities like Chennai are improving prediction and preparation abilities.

These measures, while necessary, may prove inadequate if the impacts of climate variability and a changing urban profile are not factored into disaster mitigation plans and stormwater infrastructure design. An urgent reassessment of stormwater and cloudburst management is required in India. Depending solely on drainage techniques, based on last century’s inflexible, expensive grey infrastructure, is insufficient to manage the extreme weather events of today and those expected in the future.

Cities are gradually choosing to include green infrastructure in their efforts to manage urban flooding. Studies indicate that blue-green infrastructure measures for stormwater management are cheaper and offer more co-benefits than upgrading, expanding or retrofitting traditional grey infrastructure systems. Urban planning is shifting towards water-prudent urban development and adopting integrated green and grey infrastructure solutions on the street, in their neighborhoods and across the city to build flood resilience.

Neglecting such hybrid approaches and constructing only grey stormwater infrastructure to resolve stormwater issues will not help Indian cities keep their heads above the water. Floods cause significant life, livelihood and economic losses and erode developmental dividends that city authorities accrue through decades of hard work. Water-prudent urban development coupled with integrated green and grey infrastructure can significantly increase the resilience of Indian cities against the annual flooding incidents that accompany the arrival of monsoon.

Editor's note: This article was originally published in 2020. It was last updated in July 2025 to reflect more recent data on urban flooding and built-up area.

Thanks to Samrat Basak, who contributed to the earlier version of this article.